leake



- May 31, 1927.

R. C. LEAKE STVARTING SWITCH'F'OR SINGLBPHASE MOTORS Filed Aug. 17

1920 3 Sheets-Sheet. 1

May 31,1927.

' R. .C. LEAKE STARTING SWITCH FOR SINGLE PHASE MOTORS Filed Auz. l7 1920 3 Sheets-Sheet. 2

WM WZZZQ L,

y R. c. LEAKE STARTING SWITCH FOR SINGLE PHASE MOTORS Filed Auz. 1'7 1920 3 Sheets-Sheet 3 TTOR NE Y.

FIG.7

Patented May 31, 1927.

UNITED STATES PATENT OFFICE.

' RICHARD C. LEAKE, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

STARTING SWITCH FOR SINGLE-PHASE MOTORS.

Application filed August 17, 1920. Serial No. 404,233.

This invention relates to centrifugal switches, and more particularly to a switch for starting single phase induction motors.

The principal objects of my invention are to devise a speed responsive switch of the centrifugal type which will act positively and quickly to make and break the desired circuit connections at predetermined speeds, which comprises few and simple parts easily and cheaply manufactured and assembled. and which possesses the various other features of construction and operation desirable in switches of this character; Various specific features and advantages will appear hereinafter as the description progresses.

In describing the invention in detail reference will be made to the accompanying drawings in which Figure 1 is a longitudinal diametrical sec tion through a single phase ,motor of the usual type, with my improved starting switch applied thereto;

Fig. 2 isa section taken substantially on the line 2---2 in Fig. 1' and .shows an end view of the rotor; 1 I

Fig. 3 is a transverse section. through the motor switch taken substantially on the line 3'3inFig.1; l

',Figs. 4 and 5 are sections taken substantially'on the'lines and 5-,-5 respectively in Fig.1 and looking in the direction indic'atedby thearrows; e

Fig. 6 is'a fragmentary section on the line 6- 6 in Fig. 5; and v Fig; 7'illustrates the rotor and switch diagrammatically in pers ective, with I some parts broken away and spread apart, togetlier with the circuit connections preferabiyemployed.

ferring to the accompanying drawings, I have shown my improved's'tarting switch "appliedlto a single phase motor of the usual construction comprisinga frame F, a laminated stator S with coils or windings W constituting the usual starting and running field windings forthe stator. and the rotor R fixed to a shaft 1. ,This shaft 1 is journaled in bearings supported by end caps C and C providedwith'openings for ventilation in the usual way. The upper part of the end cap Chis covered by acover or shield D having therein an insulating bushing 2 for receiving the lead or power wires for the motor} Secured to the inside face of the cap C by screws 3 (see Fig. 5) is a panel P of suitable insulating material, to which are fastened two binding posts 4 for facilitating the inter-connection of wires. The panel P is formed with a number of raised portions, preferably three in number and spaced equally around the shaft, and to each of these raised portions is fastened, by rivets or the like. a contact piece 5, of German silver, phosphor bronze, or similar material.

Cooperating with the three contact pieces 5 is a contact ring 6, preferably made of phosphor bronze, steel, or a similar comparatively hard conducting material. I prefer in most cases to make the contact ring 6 of a harder material than the contact pieces '5. The ring 6 is fastened by rivets or the like to a disc 7 of insulating material whichfits loosely on a sleeve 8 surrounding the shaft 1. The disc 7 is urged outward toward the fixed contacts '5 bya spring 9; and its outward movement is limited by a collar 10 fixed to the sleeve 8. The sleeve 8 itself isspringpressed outward by a spring 11 around the shaft 1, and to economize in' space, this spring is partly enclosed within a recess in said sleeve. Fastened to the inner end of sleeve 8 by rivetsor the like, is an irregular shaped member or'plate12. Thisplate 12 is formed with notches13 inits outer edge (see Fig. 3), three of these notches'being preferably employed. A member '14 fastened by screws 15 to the end of a rotor R is formed with arms 16 projected parallel with the shaft 1 and engaging the notches'13, so that the sleeve 8 turns with the rotor and its shaft but may slide longitudinally.

The centrifugal elements of the switch comprise a plurality of bars 17 which extend through the holes in the rotor R, such holes being commonly employed for the purpose of ventilation. In the specific embodiment illustrated. there are three of these bars 17 arranged at equal intervals around the shaft 1. One end of each bar 17 passes loosely through a slot in the plate 12, and is prevented from pulling out of this slot by a washer and small transverse pin. V The other end of each bar 17 is pivotally connected to v the end of the rotor R. The plate 20 also has fan blades 22stamped out of it.

0pe1at2'0n.'l/\" hen the rotor is at rest the parts assume the position shown in Fig. l, the sleeve 8 being pressed out by the spring 11, and the contact ring 6 being pressed into contact with the lixed contact pieces 5 by the spring The fixed contact. piccea 5 bear against the ring 6 at three points. thereby a =uring intimate contact between said ring and each contact )lLL'L'. \Vhcn the motor is started and the shaft 1 revolves, the disc 7 and the contactring (5 is held stationary by a drag upon the fixed contact pieces 5, said disc 7 slipping around the sleeve 8. As the speed of the shaft 1 increases, the bars i? tend to move outward by ci-zntritugal force, and at a predetermined critical speed, these bars are thrown outward. thereby rockin; the links 18, and pulling the sleeve 8 inward against the opposition of the spring ll. As the sleeve 8 moves inward, the tension of the spring 9 is relaxed, and linally the contact ring 6 is pulled awayfrom the fixed contact pieces 5, thereby breaking the circui-tthrough the starting \z'inding. As soon as the contact ring 6 leaves engagement with the fixed contact pieces 5, .it accelerates, and all of the arts revolvctugether with the shaft 1, without any engagement or rubbing.

When thespeed'ottheinotor falls below the critical speed, the spring llovercomes a centrifugal force exerted by the bars 1-7, and acts to returirthe parts tothe position sho vn, and again out in, the starting winding.

Referring-to Fig. 'I, 23 designates the running winding and Zl the startingwinding. When tlicswitch 25 is closed, the running winding 23 is connected directly across the supply mains 26, and the starting winding 24 is connected in multiple therewith through the contact pieces 5 and the contact disc 6, two of the contacts 5 being, prefjerably connected in multiple.

my in'iproi'ed switch is t e quick break. It will be noted One im ortantfeature of that, when the bars 17 move out-ward from the normal position shown in Fig. 1, the moment of centrifugal force about the fixed pivotal connection of the upper end of the pairs of links 18 increases, while the moment about this same pointproduccd by th spring 11 decreases. Also. as these bars move outward .their radius of gyration increases,- so that the centrifugal force exerted by these bars increases independently of the angular velocity as said bars more outward. Thus, when the centrifugal! force of the bars 17 in their inner or normal position once overcomes the tenfiioaof the spring 11, and the bars 17 start to more out, they fly out quickly, because thcy acquire an increased mechanical advantage over the spring 11 as they move out, and also'acquireanflincreased speed, and consequently, an increasing centrifugal force. This results in a quick snap movement of the contact ring 6, and serves to prevent burning or injuring ofthe contacts by long drawirout arcs. Furthermore, as the pressure of the contact ring 6 upon the tixedvcontact pieces 5 is relaxed, said ring commences to rotate, so that any are that may be drawn is-sprcad'over a comparativcly wide surface and there is no opportunity for local heating. and, pitting. lVhen the motor slows down, and the contactring (5 engages thecontaet pieces 5, said. ring rubs over said ieccstosome extent- S0 as tot-lean the sur aces and'rubdpivnnvhatever minute projections of inetal inay.have.been drawn up by arcing during the preceding opening of-the switch, with theres rltthat said contact ringv and contact pieces main; tam a scrviceableisurface after many opera:- tions. The critical speed atwhich the, switch will open: depends, upon tlie-tensionpflthe spring 11, the. weight of the barsilz the proportionin and. arrangement oi parts in general; and y .varying thesezfactors a switch may he constructed-in( accordance with my invention gn liicl jvill opciifat-any desired critical sp ocd close atsome lower critical speednl fg -i The specific construction; shgiiyhmnihde scr bed is. merely. llustrative oflmy invention and is susceptibleyof adaptation modification in 'practice. 5

' W'hat Iclaimas new'and ,desir'e toseeure. by Letters Patent, ofthe 1. In an electric motor of'thalfi'p whidh includes a shaftnnd a i otpif t-hereon,;havg h l w fi ll lng ,.t mthi iigh; .2 9 with the shafh 'a 6mprising, a plurality of. :ll: contacts arranged .aroiind gr tin shp ft a sleeve mounted on said'fsh'aft, ga g-m able axiallythereqn, a p :ing' ac tihg;tq,inpve said sleeve anfally tqpvardssaidl zconfif and an insunr dmat criiig ii-ebb sleeve r en'gas s nd-sl fir lln nnelcting said contacts, weighted at one end to said sleeve and rteiidinQIcngth \vise of the rot0,r," shafh Unto in'said-rotor, ai1d links. iygn fi jpqm'itcr a at one end to'the rotor, ldtl'i ei' end to the correspondin links extending fro in tfi'eirlpjv(ital .12 tion to the rotor'ontwardlzy', toward theirot'or. shaft, movable out-ward rad i al ly ,tp the rotor shaft about: the .;ends;c:Qiine td=-tp the sleeve and bcinganoveddengthwise by said links as the bars: mov e ohtwarglly f "2. In an electric motor of the, typflh fil includes a shaft and arotorzthereomhavin holes extending therethrough p'aranri jrfi the shaft, a centrifugal switch comprisinga 1 ,3

sleeve mounted on the rotor shaft and movable axially thereon, a spring acting to move said sleeve in one direction, circuit controlling means actuated by the axial movement of the sleeve, a plurality of weighted bars extending through said holes in the rotor and operatively connected at. one end to said sleeve, a link pivotally connected at one of its ends to the other end of each bar and at the other of its ends to the rotor, said links being inclined with respect to the axis of the rotor shaft with their ends connected to the rotor farther from the shaft than their other ends connected to said bars, whereby the axial pull of the bars on the sleeve increases as the bars move outwardly.

3. In an electric motor of the type which includes a shaft and a rotor thereon having holes extending therethrough parallel with the shaft, a centrifugal switch comprising, a plurality of contacts disposed around the rotor shaft, a sleeve mounted on the rotor shaft and movable axially thereon, a spring acting to move said sleeve toward the contacts, a contact disk rotatable on the sleeve, a spring on the sleeve acting on the disk to move it against said contacts, a plurality of weighted bars each connected at one end to said sleeve and extending lengthwise of the shaft through said holes in the rotor with their opposite ends closer to the shaft, and a link pivotally connected at one end to said opposite end of each of said bars and also pivotally connected at its other end to said rotor, said links being inclined to form with their corresponding bars an acute angle which decreases as the bars are moved outwardly by centrifugal force.

4. In an electric fnotor of the type which includes a shaft and a rotor thereon having co-operating with said contacts, a springacting to move the sleeve axially in one direction, three bars pivoted at one end to the sleeve and extending lengthwise of the rotor shaft through said holes in the rotor, and inclined links each pivotally connected at one end to the rotor arid at the other end to one of said bars, said bars when moved radially outward from the shaft by centrifugal force being shifted lengthwise by said links and acting to pull said sleeve and separate the contact ring from the stationary contacts.

5. In an electric motor of the type which includes a shaft and a rotor thereon having holes ext-ending therethrough parallel with the shaft, a centrifugal starting switch comprising, a circuit controlling element movable axiaily on the rotor shaft, a spring pressing said sleeve in one direction, a plurality of relatively long bars extending lengthwise of the rotor shaft through the holes in the rotor and connected at one end to said element, and inclined links each pi"- otally connected at one end to the rotor and at the other end to the outer free end of the corresponding bar, each bar and its link normally forming an acute angle which decrease as the bars move outward by centrifugal force.

In testimony whereof I have afiixed my signature.

RICHARD C. LEAKE. 

